A simple change in the way households use their tumble dryer could reduce the release of polluting microfibres into waterways and oceans around the world.

That is according to a new study from Northumbria University and consumer goods giant Procter & Gamble, which also shows that the equipment used to dry clothes in millions of homes may have to change. The researchers revealed that drying laundry using a condenser tumble dryer leads to hundreds of tonnes of potentially harmful microfibres being released into waterways and oceans across the UK and Europe.

The team found that while condenser dryers may reduce the volume of airborne microfibres released, compared to vented dryers, they are still a significant contributor of waterborne microfibre pollution, with more than 600 tonnes being poured down household drains.

Both types of tumble dryer produce microfibre pollution, and while condenser dryers collect moisture from wet clothes into a container, rather than exhausting it into the air as vented dryers do, the researchers found that condenser dryers in the UK and Europe still produce more than 7,200 tonnes of microfibres annually.

Down the drain

Although 91% of this material is collected in the lint filter, which many consumers dispose of in their household waste, the remaining microfibres – a massive 641 tonnes, equivalent to the weight of over 100 African elephants – are collected in the condenser and poured down the drain. This makes condenser tumble dryers a significant sources of microfibre water pollution.

Unfortunately, some appliance manufacturers suggest consumers should clean their lint filters under a tap. If consumers follow this guidance, it could lead to ten times more tonnes of microfibres entering our waterways. This means that drying is causing more waterborne microfibre pollution than clothes washing.

Bin is best

To evaluate the environmental impact of condenser dryers, Professor John Dean, from Northumbria University’s department of applied sciences, worked alongside researchers at Procter & Gamble to test loads of new, clean garments as well as dirty laundry sourced from volunteers in the city of Newcastle-upon-Tyne. They collected and analysed microfibres from several components of each type of dryer.

“We have for the first time focused on microfibre release from vented and condenser dryers using real consumer laundry loads,” said Dean. “It was found that most microfibres released from dryers is collected in the lint filter, thereby preventing release into the environment.

"However, when you realise that some manufacturers then recommend regular washing of the lint filter under a running tap, this contributes directly to an increase of waterborne microfibre pollution. After considering the environmental impact of current domestic household practices, a simple remedy is proffered.

"Instead of washing the lint filter under the tap after use in the tumble dryer, simply clean the filter either by hand, a light brush, cloth, or vacuum cleaner, and dispose of the collected fibres, as dry waste, in household waste.

"This simple and effective procedure can reduce microfibre release from tumble dryers and contribute to the protection of the global natural water environment.”

While extensive research has been carried out into the quantities of microfibres released down the drain by washing machines, historically, less has been understood about the release from tumble dryers. However, in recent years, the spotlight has shifted from the washing machine to the tumble dryer because fibres also become released from textiles during the drying process.

The team is now urging the appliance industry, its trade associations, and legislators to recognise that all types of tumble dryer can be significant contributors to the problem of environmental microfibre pollution. The researchers say that efforts are needed to mitigate this issue through revised usage instructions and improved appliance design.

Microfibre filtration

Current plans to introduce microfibre filtration systems into washing machines are expected to reduce the environmental impact of that stage in the laundering process. This study suggests that similar approaches to tumble dryers is a logical next step.

Dr Neil Lant, a research fellow at P&G and their leading scientist on this study, added, “The contribution of washing machines to aquatic microfibre pollution has now been extensively studied and filtration technology is now being integrated into those appliances to mitigate the issue.

“Our recent work in collaboration with Northumbria University has recognised, for the first time, that the most important tumble dryer types used in Europe – condenser and heat pump – can also be significant contributors to aquatic microfibre pollution, especially if users wash lint filters in a sink.

“We do over 7 billion dryer loads in the UK and EU each year, with condenser dryers generating 7,200 tonnes of microfibre. We can prevent around 90% of that from causing water pollution by cleaning lint filters into household waste, but to deal with the rest we’ll need to redesign the air filtration systems in all types of dryers.”

Procter & Gamble has been working with analytical and forensic fibre science experts at Northumbria University for over six years to improve our understanding of microfibre release during washing and drying. The complete findings of this study, The Impact of Vented & Condenser Tumble Dryers on Waterborne & Airborne Microfiber Pollution, by Northumbria University in collaboration with Procter & Gamble, are now published in the journal PLOS ONE.